1. Field of the Invention
The present invention relates to a modified ethylene resin having markedly improved wettability by water while maintaining excellent moldability and appearance of molded products inherent in the ethylene resin. The present invention also relates to an ethylene resin composition comprising a modified ethylene resin and a surfactant, the ethylene resin composition being excellent in antifogging properties and antistatic properties, particularly in permanence of these properties.
2. Background Art
Ethylene resins, such as polyethylene and ethylene/vinyl acetate copolymer, possess excellent moldability, mechanical strength, transparency, chemical resistance and other properties, and extensively used as films, sheets and the like in packaging materials, agricultural materials and the like.
The ethylene resins, however, have a nonpolar molecular structure and hence are poor in affinity for highly polar materials (hereinafter referred to as "wettability"). They, due to this nature, possess very poor antistatic properties, adhesion, paintability, printability, non-dripping properties (antifogging properties in the case of sheets and films) and other various properties. Therefore, the ethylene resins, when used as films, sheets and the like for packaging, agricultural, and other applications, permit water vapor confined in the interior to be deposited as water droplets on the inside of the films, sheets and the like, disadvantageously making it difficult to see the contents or inhibiting the transmission of sunlight, despite the fact that the transparency of the films and the sheets is maintained, or otherwise are electrified to permit dust to be easily deposited. Thus, the films, sheets and the like prepared from the ethylene resins suffer from poor antifogging properties and antistatic properties.
In order to solve the above drawbacks, incorporation of a surfactant into the ethylene resin has been carried out for a long time. This, however, causes the surfactant to bleed out in an early stage and hence cannot realize permanence of the contemplated antifogging properties and antistatic properties. Thus, imparting the antifogging properties and antistatic properties, particularly the permanence of these properties, has been a task to be accomplished in the art for a long time.
On the other hand, (graft) modification of an olefin resin with a specific modifier in order to improve the wettability of the olefin resin is known in the art.
For example, Japanese Patent Laid-Open No. 140449/1979 discloses a modified propylene resin, having improved adhesion, produced by melt-mixing a propylene resin with a compound, as a modifier, which is an ester of polyhydric alcohol with acrylic acid or methacrylic acid and has in its molecule at least one hydroxyl group, for example, polyethylene glycol (meth)acrylate having a terminal hydroxyl group, in the presence of an organic peroxide. This publication, however, does not teach the modification of ethylene resin by this method.
Japanese Patent Laid-Open No. 256430/1994 discloses a modified olefin resin produced by melt-kneading an olefin resin (particularly propylene resin) with a hydroxyl-containing .alpha.,.beta.-unsaturated carboxylic ester (for example, a (meth)acrylic ester having a hydroxyl-terminated polyethylene oxide chain or polypropylene oxide chain) and an aromatic vinyl compound (for example, styrene) as modifiers in the presence of a radical initiator. Although this publication refers to an ethylene resin as a resin to be modified, the working examples describe only modified propylene resin.
According to studies conducted by the present inventors, modification of an ethylene resin with such a modifier (grafting agent) as described in the above publications cannot provide a modified ethylene resin possessing wettability improved to a satisfactory level for practical use while maintaining good appearance of molded products. Further, as far as the present inventors know, up to now, use of the above (graft) modified olefin resin in combination with a surfactant has not been reported.